This invention relates to a test device for testing an actuator or a circuit which has an actuator without actually operating the actuator.
FIGS. 1 to 3 show prior-art test devices of this type. A test device for testing an actuator in FIG. 1 does not necessitate a testing implement. Numeral 11 designates a switch which is externally controlled in its ON and OFF positions, and numeral 20 designates a relay such as an electromagnetic relay, the input of which comprises a relay coil 21 and the output of which comprises relay contact 22, being electromagnetically coupled. Numeral 12A designates a power supply for the circuit including the relay such as an A.C. power source, numeral 31 designates an actuator which is ordinarily stopped but is operated at a selected time such as a valve, or a motor breaker, and numeral 32D designates a power supply for the actuator such as a D.C. power supply.
The switch 11, the relay coil 21 of the relay 20 and the power source 12A for the relay form a first switching circuit 10, and the relay contacts 22 of the relay 20, the actuator 31 and the actuator power supply 32D for the actuator form an actuator circuit 30.
When the switch 11 is now externally controlled to be ON, the relay coil 21 of the relay 20 is energized so that the relay contacts 22 are closed, thereby causing the actuator 31 to be operated.
In case that the actuator is very important in the operation of a plant, or that the actuator is indispensable for protecting a human body, it is necessary to test the actuator or circuit which includes the actuator periodically to determine whether they are operating normally or abnormally. When the actuator does not affect the influence to the operation of the plant even if the actuator is operated, the testing method is simple, and the actuator is actually operated as described with reference to FIG. 1.
However, when the operation of the actuator seriously affects the influence to the operation of the plant, a test device for testing the actuator is used as shown in FIG. 2.
In FIG. 2, numerals 10, 11, 12A, 20, 21, 22, 31 and 32D designate the same parts shown in FIG. 1. The test device in FIG. 2 is different from that in FIG. 1 in that a block contact 33 used at testing time, an indicator lamp 34 used at testing time and having terminals 1, 2 and 3 as well as a push-button W, and a resistor 35 have been added. The block contact 33 is normally ON, and the indicator lamp 34 is so constructed that, when a current flows from the terminal 1 to the terminal 2, the indicator lamp 34 is lit. However, when the block contact 33 is opened (OFF position), the indicator lamp 34 lights only when the push-button W is depressed, and current flows from the terminal 3 to the terminal 1. In the state shown in FIG. 2, the block contact 33 is ON, and a current, accordingly, flows from the terminal 1 to the terminal 2 of the indicator lamp 34, with the result that the indicator lamp 34 is lighted. When the block contact 33 is turned OFF and the push-button W is not depressed, no current flows through the indicator lamp 34, and the lamp 34, accordingly, is turned OFF. When the switch 11 is turned ON to carry out a test after the fact that the indicator lamp 34 is off is confirmed, the relay coil 21 is energized so that the relay contacts 22 are closed (ON position). When the push-button W is then depressed, a current flows from the positive terminal of the power supply 32D for the actuator through the terminal 3 of the indicator lamp 34, the terminal 1, the relay contact 22 and the actuator 31 to the negative terminal of the power supply 32D for the actuator, so that the indicator lamp 34 is turned ON.
A test device for testing an actuator has employed a semiconductor relay and a photocoupler as illustrated in FIG. 3 instead of the electromagnetic relay illustrated in FIG. 1 wherein, as a test implement, a pulse generating circuit serves as a power supply for testing by pulses is utilized. More particularly, numerals 11, 31 and 32D are the same as those in FIG. 1. Numeral 20D designates a photocoupler which consists of a light emitting diode 23 and a phototransistor 24 formed in such a manner that the input and the output are optically, i.e., electromagnetically coupled. Numeral 12D designates a power supply for the relay such as a D.C. power supply, the positive terminal of which is connected through a resistor 13 to the anode of the light emitting diode 23, and the cathode of this light emitting diode 23 is connected through a switch 11 to the negative terminal of the power supply 12D. A pulse generating circuit 14 for generating an ON signal is connected between both ends of the switch 11 for a short time at the testing time. Numeral 36 designates a power transistor for driving the actuator 31 by amplifying the output of the photocoupler 20D, the emitter of which is connected to the positive terminal of the power supply 32D, and the base and collector of which are respectively connected to the collector and emitter of the phototransistor 24 in the photocoupler 20D. Numeral 37 designates a current pickup for detecting in a non-contact arrangement a current which flows through the actuator circuit 30 which includes the actuator 31. Numeral 38 designates a discriminating circuit connected to the current pickup 37 for discriminating whether the second closing circuit 30 is operating normally or abnormally by amplifying the output of the current pickup 37.
The operation of the test device under normal operating conditions will be first described.
When the switch 11 is turned ON so that the light emitting diode 23 in the photocoupler 20D emits a light, the phototransistor 24 thereby conducts, and the power transistor 36 accordingly conducts, with the result that the actuator 31 is operated.
Then, the operation of the test device under test conditions will be described.
Since the switch 11 is OFF in the ordinary operating conditions, the actuator 31 does not operate. However, when a signal pulse is generated from a pulse generating circuit 14 which has a pulse width shorter than the operating time of the actuator 31, a pulse current flows through the actuator circuit 30. This pulse current is detected by the current pickup 37, and the discriminating circuit 38 discriminates between normal and abnormal actuator circuit operation from the current value and the waveform of the pulse current.
Since the prior-art test device for testing the actuator is constructed as described above, it is necessary in case of the electromagnetic relay type device to add the block contact and the indicator circuit so that the test device itself becomes complicated with the result that it was difficult to automate the testing. Further, since the prior-art test device, in the case of the semiconductor type relay, does not have a movable contact like the block contact, the automation of the testing can be facilitated, but the actuator may be accidentally operated due to malfunction in the pulse generating circuit utilized as a test implement, which is a drawback because of the danger of affecting or exerting a large influence on the plant.